Continuous process for the separation of mixtures of fatty acid esters of different melting points

ABSTRACT

THE INVENTION RELATES TO AN IMPROVEMENT OF THE KNOWN CONTINUOUS PROCESS FOR THE SEPARATION OF SOLID AND LIQUID FATTY ACID ESTERS, IN WHICH THE STARTING MIXTURE BY TREATING WITH AN AQUEOUS WETTING AGENT SOLUTION IS CONVERTED TO A DISPERSION OF LIQUID FATTY ACID ESTERS AND SOLID FATTY ESTER PARTICLES, THE FORMED DISPERSION ISSEPARATED BY CENTRIFUGING INTO TWO PHASES OF DIFFERENT SPECIFIC WEIGHTS, THE LIGHTER PHASE CONSISTS SUBSTANTIALLY OF THE LIQUID FATTY ACID ESTERS AND THE HEAVIER PHASE OF A DISPERSION OF THE SOLID FATTY ESTER PARTICLES IN THE AQUEOUS WETTING AGENT SOLUTION. AFTER SEPARATION OF THIS SUSPENSION THE WETTING AGENT SOLUTION IS RETURNED TO THE PROCESS. THE IMPROVEMENT CONSISTS IN WITHDRAWING A PART OF THE RECYCLING WETTING AGENT SOLUTION FROM THE CYCLE AND REPLACING IT WITH FRESH WETTING AGENT SOLUTION.

May 15, 1973 -H. HARTMANN ET AL 3,733,343

CONTINUOUS PROCESS FOR THE SEPARATION OF MIXTURES OF FATTY ACID ESTERS OF' DIFFERENT MELTING POINTS Filed Dec. 30. 1970 3 Sheets-Sheet 1 INVENTORS H ELMUT HART MANN WERNER ST EIN ATTORNEYS May 15, 1973 H HARTMANN ET AL 3,733,343

CONTINUOUS IHOCEJS FOR THE SEPARATION OF MIXTURES OF FATTY ACID ESTERS OF DIFFERENT MLLTING POINTS Filed Dec. 30. 1970 3 Sheets$heet 2 4 ENVEINTORS HELMUT HARTMANN WERNER STEIN ATTORNEYS May 15, 1973 H. HARTMANN ET AL 3,733,343

CONTINUOUS PROCESS FOR THE SEPARATION OF MIXTURES OF FATTY ACID ESTER$ OF DIFFERENT MELTTNG POINTS Filed Dec. 30. 1970 3 Sheets-$heet 3 INVENTORS HELMUT H ARTMANN WERNER STEIN ATTORNEYS United States Patent 3,733,343 CONTINUOUS PROCESS FOR THE SEPARATION OF MIXTURES OF FATTY ACID ESTERS OF DIFFERENT MELTING POINTS Helmut Hartmann, Langenfeld, and Werner Stein, Erkrath-Unterbach, Germany, assignors to Henkel & Cie G.m.b.H., Dusseldorf-Holthausen, Germany Filed Dec. 30, 1970, Ser. No. 102,712 Claims priority, application Germany, Oct. 30, 1970, P 20 53 257.4 Int. Cl. C09f /10 US. Cl. 260-428 '8 Claims ABSTRACT OF THE DISCLOSURE The invention relates to an improvement of the known continuous process for the separation of solid and liquid fatty acid esters, in which the starting mixture by treating with an aqueous wetting agent solution is converted to a dispersion of liquid fatty acid esters and solid fatty ester particles, the formed dispersion is separated by centrifuging into two phases of different specific weights, the lighter phase consists substantially of the liquid fatty acid esters and the heavier phase of a dispersion of the solid fatty ester particles in the aqueous wetting agent solution. After separation of this suspension the wetting agent solution is returned to the process. The improvement consists in withdrawing a part of the recycling wetting agent solution from the cycle and replacing it with fresh wetting agent solution.

THE PRIOR ART German Pat No. 977,544 discloses a process for the separation of mixtures of fatty acid esters, especially of triglyceride mixtures, into fatty acid ester mixtures of different melting points. This process involves preparing a dispersion of liquid fatty esters and separated solid fatty ester particles in an aqueous solution containing wetting agents and, optionally, non-surface-active electrolytes, and separating this dispersion with the aid of solid-jacket centrifuges into two phases of which one consists substantially of the liquid fatty acid esters and the other of a suspension of the solid fatty acid esters in the aqueous wetting agent solution. The solid fatty ester particles and the aqueous wetting agent solution are then separated in a known manner, e.g., by filtration or by melting of the until then solid fatty acid esters, so that the latter as a continuous liquid phase can be separated from the aqueous phase, The aqueous wetting agent solution, free of fatty acid esters, is then recycled in the process.

US. Pat. 2,800,493 discloses, in addition to this process for the separation of mixtures of fatty acid esters also a corresponding process for the separation of fatty acid mixtures into ingredients of different melting points. This separation principle has become known under the name Rewetting or Hydrophilization Process.

OBJECTS OF THE INVENTION An object of the present invention is the development of an improvement in the Rewetting or Hydrophilization Process whereby better separation of the higher and lower melting point mixtures of fatty acid esters are obtained continuously over long periods of time.

Another object of the present invention is the development, in the continuous process for the separation of mixtures of fatty acid esters into fatty acid ester mixtures of different melting points by the steps of continuously dispersing a mixture of fatty acid esters consisting of an oily phase and a solid phase in recycling aqueous wetting agent solution at a temperature whereby a dispersion of liquid and solid fatty acid esters is obtained, continu- ICC ously separating said dispersion by centrifuging into a lighter phase consisting substantially of liquid fatty acid esters and a heavier phase consisting substantially of solid fatty acid ester particles dispersed in said aqueous wetting agent solution, continuously withdrawing said liquid fatty acid esters, continuously separating said solid fatty acid esters from said aqueous wetting agent solution, continuously withdrawing said solid fatty acid esters having a higher melting point than said liquid fatty acid esters and continuously recycling said wetting agent solution to said dispersing step, the improvement which consist in continuously withdrawing a part of said recycling aqueous wetting agent solution and continuously replacing said withdrawn part said recycling aqueous wetting agent solution with a fresh aqueous solution whereby the concentration of said recycling aqueous wetting agent solution is maintained substantially constant.

These and other objects of the present invention will become more apparent as the description thereof proceeds.

THE DRAWINGS FIG. 1 is a flow diagram of the process of the invention.

FIG. 2 is a flow diagram of another embodiment of the process of the invention.

FIG. 3 is a flow diagram of still another embodiment of the process of the invention.

DESCRIPTION OF THE INVENTION The invention relates to an improved continuous process for the separation of mixtures of fatty acid esters, particularly of triglyceride mixtures, into ingredients of different melting points by the application of the known hydrophilization process. The process, according to the invention, is characterized in that a part of the recycling aqueous wetting agent solution is withdrawn from the cycle and the withdrawn amount of wetting agent solution is replaced by water or by fresh aqueous solutions containing wetting agents and/or electrolytes. In the event water is the replacing material, the concentration of the recycling aqueous wetting agent solution is maintained by a separate addition of the wetting agents and/or electrolytes. As a matter of simplification, in the following specification the mixture to be separated, of fatty acid esters of different melting points is called starting material, the liquid phase obtained in the separation is called oil, the solid phase obtained in the separation is called solid ingredients, and the aqueous solution used as an aid in the separation is called solution. The term solid ingredients is used for the higher melting fatty acid esters even when they are present under the then prevailing process conditions in a liquid state.

The amounts of recycling aqueous wetting agent solution to be withdrawn, or of the substituting fresh aqueous solution, are generally between more than 10% to 70%, preferably between 15% to 50% by weight of the recycling aqueous wetting agent solution. The optimum amount is dependent upon the nature of the starting material and is appropriately determined by preliminary experiments or during the continuous processing by variation of the working conditions.

The technical teaching, according to the invention, is based on the knowledge gained by internal investigations of the applicants, that in longer-lasting continuous sep arations of mixtures of fatty acid esters the results of the separation sometimes showed inexplicable fluctuations which considerably impair the value of the process for such starting materials. Presumably, differences in the nature of the starting mixtures are responsible for these fluctuations. By the invention, it now has become possible to process starting mixtures, independent of their nature, with invariable results.

The fact that in the processing of special starting materials occasionally unsatisfactory separation results are obtained, cannot be found either in the prior literature nor can it be expected from the general knowledge of the process. It is, therefore, unexpected for the applicants to have recognized this technical problem. The variant of the process, suitable for the solution of this problem, Worked out by them subsequently, has the surprising advantage that it does not require special measures outside of the hydrophilization process, such as separate special purification operations.

As starting mixtures the most varied mixed fatty acid esters of plants, animal or synthetic origin can be used. To the mixed fatty acid esters of plant origin belong, for instance, coconut fat or palm kernel fat, palm oil, cotton seed oil, olive oil, soybean oil, peanut oil, linseed oil, rapeseed oil, castor oil, etc. Mixed fatty acid esters of animal origin are, for instance, butter fat, chicken fat or goose fat, lard, mutton tallow or beef tallow, suet and bones fats as well as the large number of various fish fats and oils, blubber, whale oils, such as menhaden oil, herring oil or sperm oil, cod liver oil, etc. These mixed fatty acid esters of natural origin are mostly triglycerides, but the invention is not limited to the separation of triglycerides. -For instance, sperm oil contains, in addition to triglycerides, also fatty alcohol-fatty acid esters. Besides these, the fatty acid esters of other alcohols are to be considered as starting mixtures.

In addition to the natural triglycerides, processed products of natural fats, such as partially or completely hydrogenated fats, and ester interchange products of natural fats or esterification products of fatty acids and alcohols, where the fatty acids and/or the fatty alcohols may be of natural or synthetic origin can also be processed according to the invention.

All these mixed fatty acid esters can be processed either in the crude or the refined state. For the fats, it is a particular advantage in that they can be continuously separated in the crude state, i.e., without preceding refining.

The starting mixture can be separated, according to the invention, in two, more or less, large fractions of different melting points. Also, however, small amounts of solid ingredients can be separated from large amounts of oil, or small amounts of oil can be separated from large amounts of solid ingredients. The oil and the solid ingredients can be different or identical in regards to their degree of saturation. An example of such separations is the separation of tallow or the Winterizing from edible oils. By multiple successively arranged separations, for example, from palm oil or from ester interchange products of suitable composition, fatty fractions with properties similar to cocoa butter can be obtained.

The fatty acids present as esters in the starting mixtures contain preferably 6 to 26, particularly 8 to 20 carbon atoms. According to the invention, the esters of branched fatty acids as Well as of rosin or naphthenic acids are also included in the term fatty acid esters.

For the preparation of the dispersion of separated particles of solid ingredients and oil in aqueous wetting agent solution, appropriately a pasty mixture of crystalline solid ingredients and oil is used. The separation effect attainable, according to the invention, is dependent, among other things, upon the quality of the crystals of the solid ingredients. In order to attain a good separation, it is recommended to completely melt down the starting mixtures and then gradually cool them to the temperature at which the separation is to be effected, in order to promote proper crystal growth of the solid fatty acid esters. In the cooling of the molten starting mixture, scraping condensers have been found to be suitable. These are tubes with a cooling jacket whose inner surface is kept free of crystallizing solid ingredients by rotating scrapers. To be sure, the mixtures of fatty acid esters, to be treated according to the invention, have generally a lower speed of crystallization than corresponding mixtures of fatty acids. For this reason the fatty acid esters leave the scraping cooler mostly in a supercooled liquid state, and it is recommended to give the supercooled liquid starting mixture more time for the crystallization of the higher melting solid ingredients. An advantageous process variant has been found in which the starting material is recycled from a storage container through a scraping condenser to the storage container for a time until the complete contents of the storage container are cooled to the separation temperature. In this process variant, a heat exchange takes place between the cooled material leaving the scraping condenser and the Warmer material still in the storage container. It has been found that by this procedure a better separation results than in the process of direct cooling of the starting mixture in the scraping condenser to the separation temperature. For the crystallizing of the solid ingredients in the mixed molten fatty acid esters, other arrangements can also be used, such as standard stirring vessels.

The mixture of oil and solid ingredients thus obtained is then dispersed in the aqueous wetting agent solution which previously was appropriately brought to the separation temperature. The aqueous wetting agent solution is utilized in the amount of 0.3 to 3, preferably 1 to 2, parts by weight, based on 1 part by weight of the cooled starting mixture.

In addition to soaps, anionic or nonionic water-soluble compounds which lower the surface tension of the aqueous solutions are utilizable. A removal of the liquid ingredients of the starting mixture from the surface of the solid ingredients occurrs with the aid of the aqueous wetting agent solution. The following compounds which contain an alkyl radical with 8 to 18, preferably 10 to 16 carbon atoms in the molecule are useable in addition to soap as wetting agents: alkylbenzene sulfonates, alkylsulfonates, fatty alcohol sulfates, sulfated reaction products of fatty alcohols adducted with 1 to 10, preferably 2 to 5, mols of ethylene oxide and/or propylene oxide, monoglyceride sulfates, etc. The anionic wetting agents named are preferably used in the form of their sodium salts; but they can also be used in the form of their other alkali metal, ammonium and lower alkylolamine salts, such as potassium, ammonium, mono-, dior triethanolammonium salts. The water soluble adducts of ethylene oxide to alkylphenols or fatty alcohols are useable as nonionic compounds.

Appropriately such amounts of wetting agents are used that in the dispersion formed, immediately prior to the entry in the separation centrifuge, 0.05 to 2, preferably 0.1 to 1, parts by weight of wetting agent per parts by weight of aqueous solution are present. The above amounts for the wetting agents include not only the wetting agents actually dissolved in the aqueous phase, but also the amounts of wetting agent dissolved in the oil or adsorbed on the surface of the solid ingredients.

The effect of the aqueous wetting agent solution is improved if it contains dissolved non-surface-active electrolytes, inert to the starting mixtures. To this belong, e.g., the water soluble chlorides, sulfates, or nitrates of monoto trivalent metals, particularly of the alkali, alkaline earth and earth metals. Above all, additions of sodium sulfate and magnesium sulfate have Proven desirable. The electrolyte concentration of the dispersion, to be separated, lies in the range of 0.1% to 10%, preferably l% to 5%, by weight. These numerical data, as also above in the case of the wetting agent concentration, are calculated on the total amount of electrolytes present in the dispersion based, however, on the aqueous phase present in the dispersion. In connection with this invention, by aqueous wetting agent solution, preferably a wetting agent solution containing electrolytes is meant.

In the mixing of the cooled starting mixture with the wetting agent solution, the oil is displaced from the surfaces of the solid ingredients. It has been found appropriate to combine the cooled starting mixture first with only a partial amount of the correspondingly more contion gradually by addition of water, electrolyte solution,

or correspondingly more dilute wetting agent solution to the desired final concentration. Advantageously, the cooled starting mixture is first combined with to 50%, preferably to 30%, of the total wetting agent solution to be used, and gradually so much of further solution is added that the desired final concentration is attained. Since the wetting agent solution recycled from the process is preferably used for dilution, the wetting agent content of the more concentrated wetting agent solution to be initially combined with the cooled starting material results from the amount and wetting agent content of the wetting agent solution in the dispersion to be separated, and from the wetting agent content of the recycled wetting agent solution and also from the partial amount of wetting agent solution with which the cooled starting material is first combined.

The above-described procedure for the preparation of the dispersion to be separated can be varied in different ways. Thus, for instance, it is possible to cool the starting mixture to be separated together with the wetting agent solution, to the separation temperature. Thereby a completely melted down starting mixture can be used. In addition, the starting mixture can first, in the absence of the wetting agent solution, be cooled down so far until a part, preferably 30% to 85%, particularly 40% to 70%, by weight of the total solid ingredients, to be separated, has crystallized, and, after addition of the wetting agent solution, to further cool to the separation temperature. A special means of performing this latter process variant has proven particularly advantageous. The pre-cooled starting mixture in which solid particles have already separated is first dispersed in a partial amount of more concentrated wetting agent solution. The thus obtained more concentrated dispersion is then cooled further to the separation temperature by the addition of cooler dilute wetting agent solution, cooler water or cooler electrolyte solution and brought to the desired wetting agent and electrolyte concentration. Ice also can be used for this purpose.

In the processing of the starting mixture described so far, small amounts of air can enter into the dispersion and impair the separation result. This air can be removed simply, for instance, by slow agitation of the dispersion.

The dispersion is then passed into a solid-jacket centrifuge where it is separated into two phases of dilferent specific weights. The solid-jacket centrifuge is required to maintain the dispersion at the desired separation temperature. The most varied types of centrifuges are suitable. For instance, tube centrifuges, disk centrifuges, or shell centrifuges can be used. It can be considered an advantage that the centrifuge types utilized advantageously for a long time in the fat industry are also useable in the process, according to the invention.

Two phases leave the centrifuge: the lighter one, the oil, consists substantially of the liquid ingredients of the starting mixture, the other heavier one is a suspension of the solid ingredients in the aqueous wetting agent solution. After washing and optionally drying, the oil can be withdrawn for its designed purpose. It can also again be separated by the process of the invention at a lower separation temperature, in order to obtain thus an 011 with a suitably lower turbidity point.

The suspension of the solid ingredients in the wetting agent solution leaving the centrifuge may be processed further in various ways to separate the fatty acid esters from the aqueous wetting agent solution. Thus, the sohd particles can be separated from the wetting agent solution proper, for instance, by filtration, centrifuging, etc. It has been proven particularly appropriate to melt the solid particles by heating the suspension and to separate the thereby obtained two phases in separatory apparatus, or with the aidof other devices.

A part of the thereby obtained aqueous wetting agent solution is discarded and replaced by fresh water, by electrolyte solution, or by wetting agent solution. The amount of the recycled wetting agent solution which is to be Withdrawn and replaced by fresh wetting agent solution is dependent upon the nature of the respective starting mixture to be processed. These amounts have, therefore, to be adapted during the operation of the unit to the requirements. They have to be varied in order that the optimum improvement of the separation results in a continuous operation is attained with the lowest possible amount of wetting agent solution being withdrawn and replaced.

The wetting agent solutioin may be withdrawn at any point of the cycle, or simultaneously at several points and/or be placed by a fresh aqueous phase. Preferably, it is removed after the separation of the wetting agent solution from the melted solid ingredients.

In the enclosed FIG. 1, a flow diagram suitable for the execution of the separation process, according to the invention, is illustrated. The melted starting mixture, to be separated, is conducted through the feed pump 1 to the cooling and crystallizing apparatus 2, and leaves it as a pasty mixture of oil and solid ingredients. This mixture passes into the mixer 3 which, advantageously, consist of several mixing chambers connected in series, each of which is provided with a stirrer. In the first mixing chamber the cooled starting material is stirred up with the more concentrated Wetting agent solution, flowing in through the line 4, to give a dispersion. In the successive mixing chambers, the more dilute wetting agent or electrolyte solution is intermixed. Thereby, a dispersion is formed in which the oil particles and the particles of the solid ingredients are separately dispersed in the wetting agent solution.

This dispersion is then separated with the aid of a solid-jacket centrifuge 5 into the oil as the lighter phase and a dispersion of the solid particles in the wetting agent solution as the heavier phase. The oily lighter phase is withdrawn by line 6. The heavier phase is conducted through line 7 to the feed pump 8 which passes the material to the heater 9, where the solid ingredients are melted. The molten solid ingredients and the wetting agent solution move then together to the separator 10 from which the molten solid ingredients leave at line 11 as the lighter phase and the Wetting agent solution leaves at line 12 as the heavier phase. This heavier aqueous phase is recycled through the heat exchanger 13, through the line 14 to the mixer 3. In the process, according to the invention, a part of the wetting agent solution leaving at line 12 is withdrawn through the line 15. The corresponding amount of fresh solution is added through the line 16. It is, however, not absolutely necessary to introduce the fresh solution where in FIG. 1 the line 16 discharges in to the line 12 coming from the separator 10. Naturally, the fresh solution can be charged directly as wetting agent or electrolyte solution into the mixer 3, particularly into the successively arranged mixing chambers designed for the dilution of the first formed dispersion.

According to the invention, each of the two obtained fatty ester fractions, the lower melting (oil) and/or the higher melting (solid ingredients), can be converted to a dispersion of separated solid and liquid fatty acid ester particles in aqueous wetting agent solution, and from this a lower melting and a higher melting fatty acid ester fraction can be isolated.

If the oil, obtained in a preceding separation, is processed according to the invention procedure, it is cooled by one of the above-described methods, i.e., in the absence or also the presence of aqueous wetting agent solution, in comparison to the first separation step, to a suitably lower separation step, to a suitably lower separation temperature (cold step). The wetting agent solution circulating in the second separation step can form its own wetting agent solution cycle separated from that of 7 the first separation step. The wetting agent solution may, however, also flow through both separation steps.

The renewed application of the invention process to the oil obtained in a preceding separation step has, for example, the purpose of removing small amounts of higher melting ingredients from it, particularly to lower the turbidity point. In this case the higher melting fraction obtained as solid ingredients can be returned to the process cycle, preferably of the preceding separation step. It can, however, also be desired to separate the oil into two fractions of different melting ranges which are isolated as such in a known manner, and are used for their respective designed purposes.

If the process is applied at correspondingly higher temperatures to the solid ingredients obtained in a preceding separation step (warm step), it can be carried out according to two process variants. The one variant consists in heating the wetting agent solution with the dispersed solid ingredients in it so that a part of the solid ingredients melts and now forms an oil in this dispersion. The second variant consists in completely melting the solid ingredients and to convert them again, as described above, to a dispersion of separated particles of oil and solid particles, from which the oil and the solid ingredients are isolated, however, at a higher temperature than was the case in the first separation step. These possibilities are of particular importance there where small amounts of lower melting ingredients shall be removed from the solid ingredients obtained in the first separation step. In this case the oil fraction obtained hereby is appropriately returned to the first separation step. The process can, however, also be used to separate the solid ingredients obtained in the first separation step into two fractions with different melting points, each of which is separated and recovered for its respective use.

It is not required to withdraw wetting agent solution from the successive separation steps. However, one can also maintain a few wetting agent recycles at that point without withdrawal, these recycles being independent from the Wetting agent recycle of other separation steps, particularly of the first separation step.

Depending upon the nature of the starting mixture processed in the first separation step, it may, however, be advantageous to work also in the successive separation steps with wetting agent solutions from which partial streams are withdrawn, and which were treated with a fresh aqueous phase, i.e., with a fresh wetting agent solution, a fresh electrolyte solution, free of wetting agent, or with fresh water, free of wetting agent and electrolyte.

Since the wetting agent solution used in the first separation step consists partly of fresh aqueous phase, the wetting agent solution obtained after the first separation step may also be used in the successive separation steps.

The wetting agent solution used in a successive separation step may, however, also consist at least partly of an aqueous phase which has previously not yet been used for separation. This is always the case when a fresh aqueous phase is introduced into a successive separation step. If this wetting agent solution obtained from a successive separation step is recycled to the first separation step, a renewed withdrawal or a renewed addition of fresh aqueous phase can there be omitted.

In such a successive step, either the oil obtained in the preceding separation step or the solid ingredients obtained in the preceding separation step can be processed. The latter are preferably melted for this purpose and converted to a dispersion of separated liquid and solid fatty acid ester particles in aqueous wetting agent solution. Then the fresh aqueous phase is added to the used wetting agent solution or to the dispersion.

Insofar as the wetting agent solution used in the preceding separation step is also applied in the successive separation step, it is recommended to withdraw the part of the wetting agent solution to be withdrawn after the separation of the solid ingredients in a successive separation step, preferably in the last separation step. If there are several separation steps succeeding the first separation step, the wetting agent solution used may be withdrawn at one point or at several points simultaneously, for instance, after the first separation step, after the cold step, or after the warm step. Advantageously, the fractions obtained after the separation of the solid ingredients are combined and the desired amount of wetting agent solution is withdrawn from the combined total.

Since, according to the invention, it is irrelevant where the used Wetting agent solution is withdrawn and fresh aqueous phase is added, the exchange of wetting agent solution in the first separation step can be omitted when withdrawing the wetting agent solution after the last separation step and addition of fresh aqueous phase in a successive separation step, provided the wetting agent solution from the successive separation steps is recycled into the first separation step.

In FIG. 2, a flow diagram for the renewed separation of the oil obtained in a first separation step is illustrated schematically. The liquid starting mixture is pumped through the metering pump 1 and through the cooling and crystallizing apparatus 2. There it is converted to a pasty mixture of oil and solid ingredients, suitable for the separation. This pasty mixture passes to the mixer 3 where it is converted with more concentrated wetting agent solution (from line 4), more dilute wetting agent solution (from line 14) and electrolyte solution (from line 17) to a dispersion of separated particles of oil and solid ingredients in aqueous wetting agent solution. This mixer 3 has appropriately several mixing chambers through which successively the phases to be mixed flow, or it consists of several mixing vessels connected in series. In this way, it is possible first to combine the mixture of solid ingredients and oil with more concentrated wetting agent solution and to dilute this subsequently by the addition of more dilute aqueous wetting agent solution and/or electrolyte solution, free of wetting agent, to a lower wetting agent concentration. This dispersion flows into the solid-jacket centrifuge 5 from which at line 7, as the heavier phase, an aqueous suspension of the solid ingredients in aqueous wetting agent solution leaves, and at line 6 an oil as the lighter phase leaves.

The oil is conducted through the pump 18 into a second cooling and crystallizing apparatus 2a. The mixture of oil and solid ingredients, suitable for separation, thereby obtained is passed into a second mixing vessel 3a in which it is dispersed in aqueous wetting agent solution. For this purpose, for instance, a more concentrated wetting agent solution through line 19, a more dilute wetting agent solution through line 20, as well as, optionally, an electrolyte solution through line 21 are run in with agitation. A dispersion of separated particles of oil and solid ingredients in aqueous wetting agent solution are formed. Also this mixer 3a may have, as the one in the first step, several mixing chambers, or may consist of a number of mixing vessels, connected in series, so that also here the cooled starting material may first be combined with more concentrated wetting agent solution, which dispersion is subsequently diluted to a lower wetting agent concentration. This dispersion is passed through line 22 and is separated, as in the first step, in a second solid-jacket centrifuge 5a into the oil leaving as the lighter phase at line 23 and the suspension of solid ingredients in aqueous wetting agent solution leaving as the heavier phase at line 24.

The solid ingredients obtained as suspension in aqueous wetting agent solution at line 7 or line 24, respectively, differ in their melting points or their iodine number. Thus, for example, the solid ingredients obtained at line 7 contain less residual oil than the ones obtained at line 24. If desired, the solid ingredients obtained in the second step may be returned to the process in any way. For instance, after separation from the aqueous wetting agent solution they are admixed with the still liquid starting material leaving the cooling and crystallizing apparatus 2a. They can, however, also be processed together with the suspension obtained at line 7, as illustrated in FIG. 2. For this purpose, the combined suspensions are pumped by pump 25 through the heater 9a where they are heated to a temperature above the melting point of the solid ingredients. The mixture of molten solid ingredients and wetting agent solution is then passed into the separator 10 in which the molten solid ingredients and dilute wetting agent solution are separated. The melted solid ingredients are withdrawn through line 11 and the aqueous wetting agent solution through line 12. A part of the Wetting agent solution withdrawn from the separator 10 is discarded through the valve 26 at line 15 and thus removed from the cycle. Another part is passed through pump 27 and the heat exchangers 13 or 13a, to the controlling valves 28 or 29, and into the mixer 3 or 311.

Since a part of the recycling wetting agent solution is withdrawn at line 15 and fresh aqueous phase is added at line 17, also in the mixer 3a, a wetting agent solution is used of which a part was replaced by a fresh aqueous phase.

In FIG. 3 a flow diagram for the renewed separation, at higher and lower temperatures, of both fractions obtained in the first separation step is illustrated. The starting mixture, to be separated, is pumped by the pump 1 through the cooling and crystallizing apparatus 2 into the mixer 3. This is preferably constructed in the manner described above. It consists of single mixing chambers through which the starting mixture is successively passed. In the first mixing chamber the starting mixture leaving the cooling and crystallizing scraping condenser 2 is first combined with more concentrated wetting agent solution through line 4. Water, free of wetting agent or electrolyte solution free of wetting agent can be added through line 17, and wetting agent solution recycled from the process is added through line 14. The dispersion formed in the mixer 3 flows into the centrifuge and is there separated into two phases. The heavier phase, present as a suspension of solid ingredients in aqueous Wetting agent solution is discharged through the line 7 and the pump 8, while the lighter phase consisting substantially of oil is discharged through the line 6.

For the separation of small amounts of higher melting ingredients (cold step) still present in this oil, it is conducted through the line 6 into the mixer 3a. The latter may only consist of a simple mixing vessel. In the mixer 3a, the oil is admixed with the wetting agent solution, returned from the process through line 20. If desired, through the lines 19 or 21 more concentrated wetting agent solution and/or water, free of wetting agent, or electrolyte solution, free of wetting agent, may be supplied. The aqueous solutions added at this point may have lower temperatures than the oil. For this purpose the recycling aqueous wetting agent solution can be cooled through the heat exchanger 13a. The amount of this aqueous wetting agent solution is measured out by the valve 29. The dispersion formed in the mixer 3a, in which certain amounts of crystallized solid ingredients may already be present, is passed through the line 22 and the pump 18 into the cooling and crystallizing apparatus 2a where it is cooled to the separation temperature. From there it is passed to the centrifuge 5a from which an oil is withdrawn at line 23 as the lighter phase whose turbility point is lower than the turbidity point of the oil leaving the centrifuge 5. At line 24 a suspension of solid ingredients in aqueous wetting agent solution is obtained as the heavier phase which is pumped by pump 25 through the heater 9a and leaves it as a mixture of aqueous wetting agent solution and molten solid ingredients. In the separator this mixture is separated into the molten solid ingredient withdrawn at line 11 and the aqueous wetting agent solution withdrawn at line 12. A part of this wetting agent solution can be 10 withdrawn and discarded through the valve 26 and the line 15.

There are two possibilities for the processing at elevated temperature (warm step) of the suspension of solid ingredients in aqueous wetting agent solution leaving the centrifuge 5: either the total dispersion is heated to a temperature where a part of the solid ingredients melts, or the suspension is heated to the complete melt ing of the solid ingredients and then cooled to the separating temperature of the warm step. In the first case the pump 8 feeds the suspension, with valve 30 closed, through the open valve 31 to a combination heating and cooling apparatus 32, from which then a dispersion of separated oil and solid particles in aqueous wetting agent solution leaves. In the second case the pump feeds the suspension, with the valve 31 closed, through the open valve 30 to the heat exchanger 9 where the solid ingredients are completely melted. The emerging mixture is converted in the successively connected combination heating and cooling and crystallizing apparatus 32 to a dispersion of separated particles of oil and solid ingredients in aqueous wetting agent solution. Either of these dispersions are separated in the centrifuge 5b into the oil, Withdrawn as the lighter phase at line 33, and the suspension of solid ingredients in aqueous wetting agent solution, withdrawn as the heavier phase at line 34. The pump 35feeds this suspension into the heater 9b. The mixture of wetting agent solution and molten solid ingredients formed is separated in the separator 10a into the molten solid ingredients withdrawn at line 36 and into the aqueous wetting agent solution. The latter is withdrawn at line 37. A part of the wetting agent solution can be withdrawn from its circulation through the valve 38 and the line 39.

The part of the warm wetting agent solution leaving the separators 10 and 10a not withdrawn from circulation, is returned together to the process through the pump 27 and the line 40 and is cooled by passage through the heat exchanger 13 to the temperature at which it shall enter into the first step. The valves 28 and 29 control the partial amounts of recycling aqueous wetting agent solution which are returned to the first or to the cold step.

By the process scheme, according to FIG. 3, four fractions of ditferent melting points or turbidity points are obtained.

The following examples are illustrative of the process of the invention without being deemed limitative in any respect.

EXAMPLES The separation processes described in the following examples were carried out in a pilot plant which corresponded generally to the flow diagram of FIG. 1. The cooling and crystallizing apparatus consisted of a storage container for the molten starting mixture, from which it was pumped in a cycle over a scraping condenser and perature was reached. Subsequently, the mixture was back into the storage container until the separation temperature was reached. Subsequently, the mixture was cycled for another five hours at the separation temperature in order to secure a complete crystallization.

The data contained in the examples about the wetting agent and/or electrolyte contents are valid for the dispersion formed in the mixer in which the separated oil particles and particles of the solid ingredients were present as dispersion in the wetting agent solution. The data on the wetting agent and/or electrolyte contents include the total of the amounts of wetting agent and/or electrolyte present in such a dispersion calculated, however, on the aqueous phase.

Although the higher melting fractions obtained were present in the molten stage, for reasons of simplicity they are named as solid ingredients in the examples. The separation results obtained according to the invention are compared in the examples to those which are obtained in a similar process without the withdrawal of a part of the wetting agent solution. This procedure is indeed 1 1 known in its general characteristics, but the details described herein are derived from internal, unpublished investigations; therefore, the comparative examples are not to be considered as prior art.

EXAMPLE 1 As starting material, a palm oil (Acid No.=1.08; Saponification No.=201; Iodine No.=49) deacidified by distillation, which had been converted by cooling to a pasty mixture of crystalline solid ingredients and oil was utilized.

Comparative procedure 50 kg./h. of the palm oil, cooled to 30 C., were processed in the mixer with 40 kg./ h. of a fresh wetting agent solution at a temperatue of 31 C. which contained 3% by weight of MgSO and 0.35% by weight of sodium decylsulfate to given an aqueous dispersion which was subsequently separated in a solid-jacket centrifuge into a lighter fraction, consisting substantially of oil, and into a heavier fraction substantially present as a suspension of the solid ingredients in aqueous wetting agent solution. The latter fraction was heated to 80 C. and separated in a separator into an aqueous wetting agent solution and molten solid ingredients. The following fractions were obtained:

45.5 kg./h. of oil (ascending M.P. 31 C.; I. No.=53) 4.5 kg./h. of solid ingredients (ascending M.P. 52 C.;

I. No.=19.8.)

The aqueous wetting agent solution freed of solid ingredients, obtained in the separator, was returned after cooling to the process, with a maintained MgSO and sodium decylsulfate content. In the course of the process the separation efiect gradually deteriorated, and after 20 hours of continuous process, with the process conditions kept constant, the following separation products were obtained:

40.2 kg./h. of oil (ascending M.P. 31 C.; I. No.=53) 9.8 kg./h. of solid ingredients (ascending M.P. 49 C.;

I. No.=38)

Procedure according to the invention In the procedure described above, 34 of the 40 l./h. of aqueous wetting agent solution regained in the separator, or l./h. was discarded and replaced by 10 l./h. of a fresh 3% MgSO solution while the sodium decylsulfate content of the solution was maintained at 0.35% by weight. In this procedure no deterioration of the separation result occurred. After hours of the continuous process with the withdrawal and replacement of 10 l./h. of wetting agent solution the following separation products were obtained:

45.5 kg./h. of oil (ascending M.P. 31 C.; I. No.=53) 4.5 kg./h. of solid ingredients (ascending M.P. 52 C.;

I. No.=l9.6)

The experiments described in the Examples 2-5 were carried out substantially as described in Example 1. Insofar as deviating experimental conditions were applied, they are expressly mentioned.

EXAMPLE 2 Procedure according to the invention Starting mixture: The lower melting ingredients of palm oil (ascending M.P. 31 C., -I. No.=53) obtained in the procedure according to Example 1, were cooled to the separation temperature of 20 C. The dispersion was formed of 50 kg./h. of starting mixture, 40 kg./h. of recycled wetting agent solution, and 10 kg./h. of fresh solution. Composition of the wetting agent solution: 0.3% by weight of sodium decylsulfate, 3% by weight of MgSO Withdrawn wetting agent solution: 10 kg./h. replaced by fresh wetting agent solution with the sodium decylsulfate and MgSO content kept constant.

Process products 38 kg./h. of an oil, liquid at 20 C. (I. No.=58.5) 12 kg./h. of solid ingredients (I. No.=34, ascending M.P.=36 C.)

The solid ingredients had properties largely similar to cocoa butter.

EXAMPLE 3 Procedure according to the invention Starting mixture: Non-deacidified crude coconut oil (Acid No.=2.1; Saponification No.=259; I. No.=9.8; ascending M.P.=36 C.). The completely melted starting mixture was cooled gradually, with agitation, to 22 C. A still flowing and pumpable mixture of liquid and crystallized ingredients was formed. This mixture was used for the preparation of the dispersion.

The dispersion was formed of 50 kg./h. of the precrystallized starting mixture, 52 kg./h. of recycled aqueous wetting agent solution, cooled to 15 C., and 8 kg./h. of 4% sodium sulfate solution, cooled to 15 C.

Composition of the wetting agent solution 0.5% by weight of soap (formed from the free fatty acid of the starting mixture and small amounts of added sodium hydroxide) and 4% by weight Na SO Withdrawn wetting agent solution: 8 kg./h. replaced by Na SO solution with soap and Na SQ content kept constant.

Process products 37 kg./ h. of an oil, still liquid at 22 C. (Acid No.=12.6;

Saponification No.=255; I. No.= 10.4)

13 kg./h. of solid ingredients (Acid No.=l0.3; Saponification No.=270; I. No.=7.9; ascending M.P.=27.0 C.)

The separation results remained constant during 5 days of continuous process.

Comparative procedure When the non-deacidified crude coconut oil was treated in the same way, but with continuous recycling of the total amount of wetting agent solution, i.e., without withdrawal of part of the wetting agent solution, already after a few hours a worse separation could be observed, and after 24 hours the following process products were obtained:

24 kg./h. of an oil still liquid at 22 C. (Acid No.=12.4;

Saponification No.=255; I. No.==l0.3)

26 kg./h. of solid ingredients (Acid No.=11.4; Saponification No.=26 1; I. No.=9.3; ascending M. P.=23.5 0.).

The solid ingredients obtained hereby were substantially softer than those obtained in the procedure, according to the invention.

EXAMPLE 4 Procedure according to the invention Starting mixture: palm kernel oil (Acid No.=10.7; Saponification No.=25ll; I. No.=17.7; ascending M.P.: 28.1 C.). In contrast to the procedure described in Example 3, the starting mixture was first cooled to 245 C., whereby a part crystallized out, and the paste hereby formed was dispersed in aqueous wetting agent solution of 22 C. The temperature of the dispersion was 23.2 C. The other working conditions were identical to those in Example 3.

Process products 35 kg./h. of oil (Acid No.=l3.0; Saponification No.=

244; I. No.=22.5)

15 kg./h. of solid ingredients (Acid No.=6.2; Saponification No.=262; I. No.=7.8; ascending M.P.=32.4 C.). The solid ingredients had a dry feel and a hard, cracking break. In a continuous process of several days the separation result remained constant.

Comparative procedure In a corresponding processing of the identical palm kernel oil, but with complete recycling of the wetting agent solution, i.e., without withdrawal of part of it, a gradual deterioration of the separation result could be observed; after 30 hours the following process products were obtained:

26 kg./h. of oil (Acid No.=12.8; Saponification No.=

245; I. No.=-22.1)

24 kg./h. of solid ingredients (Acid No.=8.9; Saponification No.=257; I. *No.=l3.4; ascending M.P.=29.8 C.)

The solid ingredients were, compared to those obtained by the invention procedure, substantially oiler and softer.

EXAMPLE Procedure according to the invention Starting mixture: Crude sperm oil (I. No.=75; ascending M.P.=26.7 C.). The completely melted down starting mixture was gradually, with agitation, cooled to C. and dispersed in an aqueous wetting agent solution of 5 C.

The dispersion at a temperature of 7.3 C. was formed of 50 kg./h. of sperm oil, 60 kg./h. of recycled wetting agent solution, cooled to 5 C., and kg./h. of a fresh Wetting agent solution, cooled to 5 C., containing N21 SO and sodium dodecylbenzene sulfonate.

Composition of the wetting agent solution: 0.13% by weight of dodecylbenzene sulfonate, 2.0% by weight of Na SO Withdrawn wetting agent solution: 20 kg./h. replaced by the corresponding amount of a fresh solution containing sodium dodecylbenzene sulfonate and Na SO with wetting agent and Na SO content kept constant.

Process products:

42 kg./h. of an oil (I. No.=83; turbidity point=7 C.) 8 kg./h. of solid ingredients (I. No.=32; ascending M.P.=40 C.)

In a continuous process no deterioration of the separation result occurred after one week.

Comparative procedure In processing of the same starting mixture with recycling of the total wetting agent solution, i.e., without withdrawal of used and addition of fresh wetting agent solution, already after a few hours a deterioration of the separation result could be noticed; after hours the following process products were obtained:

35 kg./h. of an oil (I. No.=82.7; turbidity point=7 C.) 15 kg./h. of solid ingredients (I. No.=No.56; ascending M.P.=32 C.)

It can thus be seen that the continuous process of the invention with the constant withdrawal of part of the recycling aqueous wetting agent solution and its replacement with fresh aqueous wetting agent solution results in clean separation of oily from solid fats over long periods of operation without deterioration of the separation results.

The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, how ever, that other procedures known to those skilled in the 14 art may be employed without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. In the continuous process for the separation of mixtures of fatty acid esters into fatty acid ester mixtures of different melting points by the steps of continuously dispersing a mixture of fatty acid esters consisting of an oily phase and a solid phase in a recycling aqueous wetting agent solution at a temperature whereby a dispersion of liquid and solid fatty acid esters is obtained, continuously separating said dispersion by centrifuging into a lighter phase consisting substantially of liquid fatty acid esters and a heavier phase consisting substantially of solid fatty acid ester particles dispersed in said aqueous wetting agent solution, continuously withdrawing said liquid fatty acid esters, continuously separating said solid fatty acid esters from said aqueous Wetting agent solution, continuously withdrawing said solid fatty acid esters having a higher melting point than said liquid fatty acid esters and continuously recyling said aqueous wetting agent solution to said dispersing step, the improvement which consists in continuously withdrawing from 10% to by weight of said recycling aqueous wetting agent solution and continuously replacing said withdrawn part of said recycling aqueous wetting agent solution with a fresh aqueous solution whereby the concentration of said recycling aqueous wetting agent solution is maintained substantially constant.

2. The process of claim 1 wherein the amount of said recyling aqueous wetting agent solution withdrawn is from about 15% to 50% by weight of said recyling aqueous solution.

3. The process of claim 1 wherein said recycling aqueous wetting agent solution contains electrolytes.

4. The process of claim 3 wherein said fresh aqueous solution continuously replacing said withdrawn part of said recycling aqueous wetting agent solution has the same concentration of wetting agent and electrolyte as said recyling aqueous wetting agent solution.

5. The process of claim 3 wherein said fresh aqueous solution continuously replacing said withdrawn part of said recycling aqueous wetting agent solution is water and said concentration of said recycling aqueous wetting agent solution is maintained constant by separately continuously adding wetting agent and electrolyte.

6. The process of claim 1 wherein said mixture of fatty acid esters is unrefined crude fats.

7. The process of claim 1 wherein said mixture of fatty acid esters is a liquid fatty acid ester mixture previously separated by the process.

8. The process of claim 1 wherein said mixture of fatty acid esters is a solid fatty acid mixture previously separated by the process.

References Cited UNITED STATES PATENTS 2,325,327 7/ 1943 Lachle 260412 2,622,114 12/1952 Carney 260-412 2,663,717 12/1953 Strezynski et al. 260412 2,773,889 12/1956 Kao 260412 2,823,214 2/ 1958 Sharples 260412 LEWIS GOTTS, Primary Examiner J. R. BROWN Assistant Examiner 

